1. Technical Field
The present invention relates to a template pulse generating circuit, a communication device, and a communication method well adapted to ultra wide band (UWB) communication, and in particular to a template pulse generating circuit, a communication device, and a communication method arranged to achieve low power consumption in a receiving system.
2. Related Art
In the UWB communication, very wide-band communication method using very short-period pulses is also called UWB impulse radio (UWB-IR) communication. In the UWB-IR method, modulation/demodulation can be performed only by a time base operation without using a past modulation method, and consequently, it is conceivable that simplification of the circuit and low power consumption can be expected (see e.g., JP-T-2004-528776 (paragraphs 0035-0040, FIG. 5) (hereinafter, Document 1), and JP-T-2005-517355 (paragraphs 0015-0020, FIG. 20) (hereinafter, Document 2)).
Further, it is proposed that in a receiving device for receiving a transmission signal composed of a pulse signal train, a template pulse with substantially the same generation interval as the transmission pulse is generated by a pulse generating section, the generation position of the template pulse is shifted in phase a predetermined distance by a phase shifting section, each of the template pulses thus shifted in phase and the received pulse are correlated with each other by a correlation section, and the synchronization capturing to the received signal is performed based on the correlation result (see JP-T-2004-241927 (paragraphs 0025-0028, FIG. 1) (hereinafter, Document 3)).
Further, there is presented a propose for achieving reduction of power consumption by controlling the generation position of the template pulse and stopping the receiving circuit in a period when no receiving pulse arrives (JP-A-2005-217899 (paragraphs 0023-0026, FIG. 1) (hereinafter, Document 4)).
As described above, although in the UWB communication, owing to the nature thereof, low power consumption communication can be realized, in the proposals described in the Documents 1 through 3 mentioned above, there is presented neither recognition of a technical problem of reducing the power consumption beyond the extent normally obtained by applying the present communication method, nor a particular proposal regarding a solution to such a technical problem, consequently.
Further, although the proposal for achieving reduction of the power consumption is disclosed in the Document 4, it seems impossible for the technology described in the document to achieve lower power consumption in a process for capturing synchronization by searching presence of the pulse itself from the condition in which timing of the arriving pulse is unknown.
In other words, also in the Document 4, there remains a technical problem that since in the process for capturing synchronization by searching presence of the pulse itself, the timing of the incoming pulse is searched while sequentially shifting the phase of the template pulse generated on the receiving side, the synchronization capturing takes time, and the power consumption is also increased correspondingly to the time.